The present invention relates to an automatic combinatorial weighing apparatus.
Automatic combinatorial weighing devices operate by supplying articles to be weighed to a plurality of weighing machines, effecting a combinatorial arithmetic operation based on weights detected by the weighing machines, selecting an optimum weight combination with a combined weight equal or closest to a target weight, and discharging the articles from only those weighing machines which give the optimum weight combination, thereby obtaining a group of articles having their combined weight equal or closest to the target weight.
One such automatic combinatorial weighing apparatus will be described with reference to FIG. 21 of the accompanying drawings. The automatic combinatorial weighing apparatus, generally denoted at 1, has a frame 2 and a subframe 3 disposed above the frame 2 and supported thereon by a plurality of legs 2a. A distributing or dispersing table 4 is mounted centrally on the subframe 3 using an electromagnetic three-dimensional vibrator 5. The weighing apparatus 1 includes a plurality (14, for example) of heads comprising respective radial troughs 6 disposed around the distributing table 4 and mounted on the subframe 3 by respective electromagnetic vibrators 7. A plurality of pool hoppers 8 are positioned respectively outside and below the radial troughs 6, and a plurality of weighing hoppers 10 are disposed below the pool hoppers 8, respectively, the weighing hoppers 10 being supported by a plurality of weighing devices 9, respectively. The pool hoppers 8 and the weighing hoppers 10 have respective lids which can be opened and closed by link mechanisms 16 through push rods 14 of opening and closing devices 13 mounted on the lower surface of the subframe 3. The opening and closing devices 13 can be actuated through a gear transmission device 12a by a motor 12 mounted centrally on the lower surface of the subframe 3.
Collection chutes 11 are mounted on the frame 2 below the weighing hoppers 10 for collecting the articles discharged from the weighing hoppers 10 and discharging the collected articles to a packaging device (not shown).
The automatic combinatorial weighing apparatus thus constructed operates as follows: Articles to be weighed are dropped from an article feeder (not shown) onto the distributing table 4 and distributed thereby into the radial troughs 6, from which the articles are supplied to the pool hoppers 8, respectively. The articles are then fed from the pool hoppers 8 into the respective weighing hoppers 10 and weighed therein by the weighing devices 9, respectively. Weight signals from the weighing devices 9 are applied to an arithmetic control unit (not shown), which effects a combinatorial arithmetic operation based on the weight values represented by the applied weight signals. The arithmetic control unit then selects an optimum weight combination with a combined weight equal or closest to a target weight, and controls the opening and closing devices 13 to open the lids of those weighing hoppers 10 which contain the articles giving the optimum weight combination, thereby discharging the articles from the selected weighing hoppers 10. The weighing hoppers 10 from which the articles have been discharged are then supplied with articles from the corresponding pool hoppers 8, which are in turn supplied with articles from the corresponding radial troughs 6.
The arithmetic control unit comprises a microcomputer for effecting the combinatorial arithmetic operations necessary to enable the automatic combinatorial weighing apparatus 1 to weigh articles at high speed.
To assist the automatic combinatorial weighing apparatus 1 in operating at high speed the electronic controls, the pool hoppers 8 and the weighing hoppers 10 are arranged in a circular pattern of a small diameter around the central vertical axis of the apparatus 1, i.e., the apparatus 1 has a reduced diametrical size, so that the aritcles will fall and slide along a short path and at high speed. The vertical dimension of the apparatus 1 is also reduced to shorten the path along which the articles fall through the apparatus 1.
As illustrated in FIG. 21, the pool hoppers 8 and the weighing hoppers 10 are arranged such that the collection chutes 11 for delivering the articles fed from the weighing hoppers 10 through timing hoppers 110 to the packaging process are of the greatest size among other components. Since the hoppers 8 and 10 are circularly arranged, the diameter of the collection chutes 11 can not be reduced beyond a certain limit. In addition, if the collection chutes 11 were excessively reduced in their height, their slide surfaces have too a small gradient and impose a large resistance to the sliding movement of the articles thereon, thus preventing higher-speed operation.
Since the lids of the weighing hoppers 10 are openable outwardly and inwardly as shown in FIG. 21, one of the collection chutes 11 is positioned as an inner collection chute for receiving articles through the inwardly openable lids of the weighing hoppers 10 and the other as an outer collection chute for receiving articles through the outwardly openable lids of the weighing hoppers 10. The lids of the weighing hoppers 10 are opened alternately inwardly and outwardly to supply articles to the double collection chute assembly for higher-speed operation.
One requirement for achieving higher-speed operation and removing obstacles against such higher-speed operation in the double collection chute assembly is that the articles discharged from the weighing hoppers 10 be fed along straight paths of least resistance to their sliding movement in the inner and outer collection chutes.
The inner and outer collection chutes are coaxially arranged and required to have their own outlets or timing hoppers 110. Various improvements have heretofore been made to shorten the path of sliding movement of the articles down the inner and outer collection chutes toward their lower outlets.
There has been developed a double collection chute assembly as shown in FIG. 22 of the accompanying drawings. The double collection chute assembly, generally designated at 11 in FIG. 22, has an inner collection chute 111 in the form of a truncated cone and outer collection chutes 112 each in the form of a substantially semicircular cone, the outer collection chutes 112 being symmetrical with respect to a plane S passing through the center of the inner collection chute 111. The inner collection chute 111 has an outlet 113 offset or displaced from the central axis and connected to inclined off-center discharge chutes 114, 115. The outer collection chutes 112 and the inner collection chute 111 create discharge clearances 116 therebetween, which are connected to outlets 117 joined to a downwardly tapered discharge chute 118 having an outlet 120. The inner collection chute 111 has an outlet 119 which is disposed as closely to the outlet 120 as possible. The shapes, sizes, and positions of the inner and outer collection chutes 111, 112 are substantially similar such that the articles falling down the inner collection chute 111 and discharged into the clearances 116 will slidingly drop as quickly as possible over the shortest distance.
With the double collection chute assembly 11, the articles are theoretically assumed to fall quickly down the inner and outer collection chutes 111, 112 and reach the outlets 119, 120 at the same speed in the same period of time. However, the articles tend to hit each other and be caused to jump and flow in meandering or roundabout paths because the slanted surfaces of the chutes 111, 112 are curved. Particularly, while the articles falling in the clearances 116 drop through the discharge chute 118 beneath the outlets 117 to the outlet 120, the articles are forced to flow in a curved path on the inner side of the discharge chute 118, with the result that the articles are caused to flow around about and are apt to be disturbed just before the outlet 120. Therefore, the articles falling down the discharge chute 118 are more likely to flow down at irregular speeds in uneven times than those falling down the discharge chutes 114, 115 of the inner collection chute 111 in which the articles fall more smoothly.
The outer collection chutes 112 are not symmetrical with respect to a plane P normal to the plane S. Therefore, the articles falling on the opposite sides of the plane P fall in different paths and at different speeds in different time periods.
A number of such combinatorial weighing apparatus 1 are generally employed in a packaging center or the like, where mainly foods are processed by the weighing apparatus 1 and where the building of the packaging center is closed to the exterior. When all of the combinatorial weighing apparatus 1 are operated at the same time, much noise is produced by the vibration of the combinatorial weighing apparatus 1 and noise is also produced in a high-frequency range due to hitting engagement of the articles with panels and plates of the apparatus 1 and the resonating vibration of these panels and plates. The combined noise level is intolerably high in the building and hence the working environment is poor. At times, accurate measurements and communications are hindered by such a high noise level.
More specifically, the articles supplied onto the distributing table 4 of the automatic weighing apparatus 1 are delivered from the radial troughs 6 to the pool hoppers 8 to the weighing hoppers 10 to the collection chutes 11. Since the lids of the hoppers 8, 10 are intermittently opened and closed, the articles are caused to follow stepped, irregular and curved paths such as zigzag paths as the articles are charged and discharged.
Since there are many heads in the combinatorial weighing apparatus 1, the articles are caused to flow through the stepped, irregular and curved paths while the heads are operated in and out of synchronism. Accordingly, a considerably high degree of noise is produced in an area where many combinatorial weighing apparatus 1 are arranged in an array.
The higher the speed of delivery of the articles through the apparatus 1, the larger the noise produced thereby. The noise becomes much larger if the collection chutes are improved for higher speed of flow of the articles through the apparatus 1.
One known approach to solving the noise problem has been to line or coat the surfaces of the pool hoppers 8 hit by the articles as they are disharged radially outwardly from the radial troughs 6 and also to coat surfaces of the lids of the weighing hoppers 10 hit by the articles as they are discharged downwardly obliquely from the pool hoppers 8, with urethane layers or urethane sheets for cushioning the articles to attenuate the noise produced thereby.
However, the sound-insulating materials used in the above arrangement are not sufficiently capable of against insulating noise. To prevent the lining or coating layers from being peeled off when the weighing apparatus 1 are cleaned or operated highly frequently, the lining or coating layers should be of a considerable thickness. These thick layers are practically unacceptable in recent weighing apparatus which are required to be compact and complex in their internal structure. In addition, the cost of attaching the lining or coating layers to the complex structural members is prohibitively high.